Have you wondered what is that cloud?
Weather and clouds, in particular, are both incredibly fascinating. Just as the weather comes in many different forms so do clouds.
Along with their beauty clouds provide an indication of what potential weather conditions may be on the way.
While there are 100’s of cloud formations the are 10 main classifications. By knowing these 10 classifications you can get a better idea of what is happening in the atmosphere.
As a pilot, knowledge of the weather is more than essential it is a requirement.
Formations of clouds
When they appear they provide us with a visual show that there is water in the atmosphere. Millions of tons of water evaporate into the air each day from oceans, rivers, and from transpiration from plants and trees.
When moist air rises it meets low pressures which cause it to expand and cool. As it cools it holds less water vapour and will become saturated. This is when some of the water vapour condenses to tiny droplets which are 1 million times smaller than a raindrop. These tiny droplets form clouds.
Classifications of clouds
The 10 main cloud types are further divided into 27 sub-types based on their height, shape, colour and associated weather. Clouds are generally categorised by where they sit in the atmosphere:
- Low—from the earth’s surface to 2.5km
- Middle—2.5 to 6km
- High—above 6km
Latin names describe their characteristics
- Cirrus (a hair)
- Cumulus (a heap)
- Stratus (a layer)
- Nimbus (rain-bearing)
All clouds are actually white in colour, but when viewed from the ground some appear grey or dark grey according to their depth and shading from higher cloud.
You’ll generally notice two different appearances of clouds—layers of cloud that look like sheets, and clumpy clouds that look like smoke plumes.
Clouds – Layers and Clumps
The layer cloud types are known as stratiform and are classified as:
- Stratus —found in the low levels of the atmosphere, tend to produce a light drizzle.
- Altostratus —(‘alto’ meaning high), found in the middle level, tend to be a very good rain-producing system for large areas across Australia, particularly inland.
- Nimbostratus —formed when altostratus undergoes further vertical development, allowing the cloud to hold more moisture, and causing the cloud base to lower and produce heavier rainfall; also appears darker in colour.
- Cirrostratus —found in the higher levels of the atmosphere, white and wispy, and made of ice crystals. We often get a lot of halo activity with cirrostratus cloud, with the ice crystals refracting light around the moon and the sun.
The clumpy cloud, when in the lower part of the atmosphere, is classified as cumulus cloud:
- Cumulus —a low-level cloud which tends to produce short duration, fairly intense rainfall that is often very localised, meaning that rain falling at your house might not be falling at your neighbour’s a kilometre up the road.
- Stratocumulus —found in the lower levels, a blend between stratiform and cumuliform cloud and taking on appearances from both these cloud types, may produce drizzle.
- Altocumulus —found in the middle levels, looks like sheep in the sky, may produce light showers.
- Cirrocumulus —small, rippled, higher-level cloud, does not produce precipitation.
- Cumulonimbus —the largest cloud of all, forms in the lower layer of the atmosphere but extends through all three layers right to the top of the atmosphere. Also known as thunderstorm cloud, producing thunder and lightning.
Some of the more visually spectacular clouds happens very high up in the atmosphere, and is classified as cirrus cloud:
- Cirrus —formed of ice crystals moving very quickly through the atmosphere, occurring at temperatures around –40°C to –60°C, does not produce precipitation.
Which type of clouds do you love to see?
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Reference: Bureau of Meteorology